1. Field of the Invention
The invention relates to semiconductor devices. More specifically, the present invention relates to the production of semiconductor devices where wet chemical treatments are used on a wafer with high aspect ratio nanostructures that are sensitive to pattern collapse during processing.
2. Description of the Related Art
Semiconductor devices are fabricated using a long complex procedure. One portion of the procedure involves etching features into a stack of materials on a silicon wafer. The stack of materials may comprise a single layer of silicon based material such as SiO or SiN, or the stack may comprise multiple layers of materials such as SiO, SiN, TEOS, polysilicon or silicon in different orders within the stack. The stack may be formed by a number of methods, including physical vapor deposition, chemical vapor deposition, electrochemical deposition and molecular beam epitaxy, for example. Once the stack of materials is created, a photoresist layer is applied. This photoresist layer is used as a mask for etching. Many methods of etching may be used including methods of wet etching and dry etching. After the etching, the photoresist layer is usually removed, often by a plasma ashing procedure.
During the fabrication, the wafers are subjected to wet processing such as wet cleaning. Wet cleaning is helpful to prepare the surfaces and to remove residue left behind by some of the other processing. The cleaning process usually consists of chemical treatment in combination with megasonics, jets and/or other particle removal techniques followed by rinsing and drying. The drying may include bulk liquid removal from the surface by spin off, vacuum suction, Marangoni effect with isopropyl alcohol or combination of these commonly known techniques
A wafer may go through multiple occurrences of these steps during the entire fabrication process. Hence, as device features shrink on a wafer and as much liquid is used in the processing, strong capillary forces may exert enough force to collapse the structures during drying steps.